1. Field of the Invention
This invention relates generally to exercise machines, and is particularly concerned with an exercise machine for performing shoulder press exercises which has a moving user support.
2. Related Art
Free weight shoulder press exercises using barbells or dumbbells involve an exerciser in a standing position holding dumbbells at a position just above their shoulders, and then raising the weights over their head. The free standing shoulder press movement is one of the most fundamental exercises and is one of the standard measures of strength. However, it can be difficult for many people to perform. It requires balance and coordination as well as strength for someone to raise a weight or weights over their head with a slight arcing motion while maintaining balance. This is a compound or multi-joint movement which involves the front and outer deltoid muscles of the shoulder. Improper form during the exercise (jerking or swinging the weights upward, leaning forward or arcing backward) can throw the exerciser off balance, which makes the exercise more difficult, increases stress to the joints, and can lead to possible injury.
In order to help the less conditioned exerciser perform this basic exercise, the seated shoulder press bench was developed. This provided stabilizing support by placing the user in a seated position with back support, preventing the user from swinging the weights, walking with the weights, or arching their back while performing the exercise. A further safety development replaced the free weight movement with a machine utilizing an exercise arm pivotally attached to the stationary bench or user seat. Such machines typically have an exercise arm movably mounted on a stationary frame with a seat and back pad or user support rigidly mounted on a stationary frame, with plate loading, selectorized weight stack, hydraulic, pneumatic or elastic bands for resistance.
Some known shoulder press exercise machines are described in U.S. Pat. No. 5,554,089 of Jones, U.S. Pat. No. 5,810,701 of Ellis, and U.S. Pat. No. 5,562,577 of Jones. Each of these machines has a main frame, a user support rigidly mounted to the main frame, and a plate-loaded exercise arm pivotally mounted on the main frame. All three of these machines have exercise arms that provide a converging exercise motion, because the user engaging handles are forced inwards as the exercise arm is urged upward in performing a shoulder press exercise. Each of the machines has weight receiving pegs on the outboard side of the exercise arm, increasing the overall size of the machine and creating a safety hazard as the weight swings during exercise machine use. Jones and Ellis provide an exaggerated arc in the exercise motion, preventing the user engaging handles from ending up in line with the side centerline of the user's body at the end of the exercise, as is the case with the free weight shoulder press.
U.S. Pat. No. 4,844,456 of Habing describes a machine providing multiple exercises, including a forward inclined shoulder press. Again, the user support is fixed in position, and an exaggerated arc is provided by the pivoting exercise arm. Back supported shoulder press exercise capability is also provided in the machines described in U.S. Pat. Nos. 5,447,480 and 5,549,530 of Fulks, but again the pivoted exercise arm provides an exaggerated arc and prevents the user engaging handles from ending up in the optimum finish position for a shoulder press exercise. U.S. Pat. No. 6,080,091 of Habing describes an exercise machine with a pressing arm assembly comprising a main arm pivotally mounted on the main frame and two handle arms pivotally coupled to the main arm cross beam. The handle arms can pivot freely inwardly and outwardly. The exercise resistance, in this case a weight stack, is associated with the main arm. This design provides a straight pressing motion as well as an inward converging press motion and an outward to inward “fly” motion. Again, the user seat or support is fixed in position on the frame.
Some known multi-purpose exercise machines for performing various different types of exercise have movable seats or user supports. In U.S. Pat. No. 5,330,405 of Habing, the machine has a stationary base frame, a lever arm pivotally mounted on the frame, and a sub frame pivotally connected to the base frame and supported by the lever arm. The sub frame comprises a user support and an exercise arm linked to the lever arm by cables and pulleys. The exercise arm for performing pressing exercises is pivotally connected to a portion of the sub frame at a location above the user. In order to perform a shoulder press, the user must sit on the user support leaning forward at an angle without benefit of back support, pressing the exercise arm forward and rotating it about its pivotal connection to the sub frame in order to pull the cables and cause the sub frame to lift.
U.S. Pat. No. 5,669,865 of Gordon describes a multi-purpose user support with a hinged, two-piece user support that folds and unfolds with each exercise repetition. The user support comprises a seat portion and a back portion which are pivotally connected together, and is pivotally connected to the main frame. A first exercise arm pivoted to the frame provides pressing and pull down exercises. The seat and back rest do not travel in a fixed relationship to each other, but fold and unfold during the exercise, working the abdominal and low back muscles even when other exercises are being performed. Due to the separate motion of the seat and back rest, additional supports such as a foot rest, safety belts, and thigh gripping surfaces are required to keep the user properly and safely positioned. In this machine, most of the combined weight of the user and user support remains on one side of the gravitational centerline of the user support, and this weight is used as a partial exercise resistance. Due to the working of the abdominal and low back muscles in every exercise movement, including press exercises, the exerciser cannot properly isolate any one specific muscle or muscle group. Because of this, the exerciser cannot fully fatigue other muscles, since the abdominals and lower back will always fatigue first.
None of the prior art exercise machines for performing shoulder press exercises properly simulate the slight arcing motion as well as the start and finish positions found in a free weight shoulder press exercise, while properly supporting the user's body throughout the exercise movement. Most or all shoulder press exercise machines with fixed user supports have an exaggerated and unnatural arcing movement during the exercise, and do not provide the proper starting and finishing alignment between the user and exercise arm handles.